1. Field of the Invention
The present invention relates to an industrial robot which is provided with a rotatable robot main body, a first robot arm which is mounted, via a first joint portion, on an upper end of the robot main body so as to be swingable in the vertical direction, and a second robot arm which is mounted, via a second joint portion, on a front end of the first robot arm so as to be swingable in the vertical direction.
2. Description of the Related Art
Conventionally, in this kind of industrial robot, it is normal practice to constitute each of the joint portions by a construction in which each of the robot arms is supported on both axial sides of each of the joint portions. This construction has, however, disadvantages in that the construction of the joint portions becomes complicated and that the assembly thereof becomes troublesome.
In order to solve the above-described disadvantages, there is known an industrial robot as disclosed in Japanese Published Unexamined Patent Application No. 27685/1982. In this industrial robot, a first joint portion at an upper end of a robot main body and a second joint portion at a front end of a first robot arm are constituted in a cantilevered construction in which the first robot arm and the second robot arm are respectively supported, via a driving reduction gear, in a manner cantilevered in the axial direction of each of the joints. It is thus so arranged that each of the robot arms can be assembled to each of the joint portions from one axial side thereof to facilitate the assembling.
In the above-described conventional industrial robot which is provided with joint portions of cantilevered construction, the first robot arm and the second robot arm are respectively mounted on the robot main body and on the first robot arm in a manner offset to one axial side of each of the joint portions. Partial loads due to this offset will thus operate on the robot main body. This industrial robot has therefore disadvantages in that the positioning accuracy of the robot will be adversely affected and that the teaching of the robot becomes troublesome.
In view of the above-described points, the present invention has an object of providing an industrial robot in which each of the joint portions is made in a cantilevered construction to facilitate the assembling, and in which the above-described disadvantages associated with providing the joint portions of a cantilevered construction are eliminated.